1. Field of the Invention
The present invention relates to a liquid crystal display with an EL (electroluminescent) backlight.
2. Description of the Related Art
FIG. 7 is a whole sectional view showing a conventional liquid crystal display. FIG. 8 is a assembly perspective view showing an EL backlight in the liquid crystal display shown in FIG. 7.
A conventional liquid crystal display 50 includes a liquid crystal display panel 54 provided with multiple openings 52 allowing adjustable light transference quantity and an EL backlight 56 being an approximate size of the liquid crystal display panel 54 and irradiating the liquid crystal display panel 54 from the back of the liquid crystal display panel 54.
The liquid crystal display panel 54 is an active matrix using a TFT (thin film transistor) or a like. The active matrix is a liquid crystal inserted between two glass plates, each of which is provided with a transference electrode, the TFT and a color filter inside and deflecting plates are provided covering outsides of the glass plates. Each of the openings 52 corresponds to one pixel. A non-opening 57 in the vicinity of the opening 52 is formed with a metal electrode, a black matrix or a like and shields light.
The EL backlight 56, as shown in FIG. 8, is structured by inserting a flat sheet in which a surface electrode (transference electrode) 58, a luminous layer 60, an insulating layer 62 and a rear face electrode 64 are laminated between a moisture-proof film 661 and a protective layer 681 and a moisture-proof film 662 and a protective layer 682. The surface electrode 58 is connected with a current collecting band 701 and a electrode lead 721, and the rear face electrode 64 is connected with a current collecting band 702 and a electrode lead 722.
The EL backlight 56 is a surface light source, therefore, it is possible to irradiate all of openings 52 directly without a light-introducing plate or a like. At each of the openings 52, a light transference quantity is adjusted in response to an image signal and then an image is displayed on the liquid crystal display with this light transference quantity adjustment.
Further, since the light from the EL backlight 56 is non-directional, the light is also irradiated equally to non-openings 57 and to the openings 52. Therefore, to use the light from the EL backlight 56 effectively, it is necessary to put a condensing unit such as a lens sheet 74 (shown in FIG. 7) between the liquid crystal display panel 54 and the EL backlight 56. The lens sheet 74 is provided with small lenses corresponding to the respective openings 52 and converges the light from the EL backlight 56 to the respective openings 52.
Each of Japanese Utility Model Application Laid-Open No. Sho63-120233 and Japanese Patent Application Laid-Open No. Hei3-74084 shows a liquid crystal displays provided with a concave and convex luminous surface of an EL backlight to improve luminance per an unit-surface-area. In this case, light from the EL backlight is also non-directional, therefore, it is also necessary to use a condensing unit such as a lens sheet to use the light of the EL backlight effectively.
However, a condensing unit such as a lens sheet prevents a liquid crystal display from reducing thickness, weight, a number or parts or a like.
In view of the above, it is an object of the present invention to provide a liquid crystal display utilizing a light from an EL backlight effectively without a condensing unit such as a lens sheet.
According to a first aspect of the present invention, there is provided a liquid crystal display including a liquid crystal display panel provided with multiple openings allowing adjustable light transference quantity; an EL backlight being an approximate size of the liquid crystal display panel and irradiating the liquid crystal display panel from back of the liquid crystal display panel; and concave luminous parts respectively corresponding to the openings in a luminous layer of the EL backlight.
Light generated in one of the concave luminous parts is repeatedly reflected by an inner wall of the concave luminous part and goes out along a central axis of the concave luminous part. An opening corresponding to this concave luminous part is positioned in a same direction as the central axis direction of the concave luminous part. Therefore, the light generated in the concave luminous part has a strong directivity to the opening corresponding to the concave luminous part. That is to say, the EL backlight operates equally to a condensing unit such as a lens sheet. Moreover, with this structure, an area of a luminous layer for one opening is larger than a case in that light is condensed from a flat luminous layer to one opening, therefore, luminance is improved.
In the foregoing, a preferable mode is one wherein each of the concave luminous parts is formed for each of the openings. Though two or more concave luminous parts may be formed for one opening; one-to-one is easier.
Also, a preferable mode is one wherein each of the concave luminous parts is formed for each of the openings and a center of each of the concave luminous parts coincides with a center of each of the openings when the liquid crystal display panel is viewed from front. With this mode, it is possible to introduce the light of the concave luminous parts to the opening most effectively.
Also, a preferable mode is one wherein a protective layer with a flat surface is filled in the concave luminous parts, and when a distance between the liquid crystal display panel and the EL backlight is defined as L, a pitch of the openings is defined as P1, a pitch of the concave luminous parts is defined as P2, a size of one of the concave luminous parts is defined as D. When an area surrounded by a peripheral edge of the concave luminous part is defined as S, D=2xe2x96xa1(S/xe2x96xa1) (formula (1)) is expressed. When a critical angle to the protective layer is defined as xcex80, P1=P2 and L xe2x96xa1 (D+(P2xe2x88x92D)/2)xc3x97tan(90xc2x0xe2x88x92xcex80) (formula (2)) is expressed. In this mode, it is possible to introduce the light of the concave luminous part effectively. A shape of the peripheral edge of the concave luminous part may be a circle, an ellipse, a triangle, a polygon or a like. Incidentally, a size D except for the circle is approximated by the formula (1).
Also, a preferable mode is one wherein the concave luminous parts are formed in a higher-density as luminance becomes lower and are formed in a lower-density as luminance becomes higher in the flat luminous layer of the EL backlight. In this mode, the luminance of the EL backlight becomes unity. For example, a lower luminous part is in a vicinity of the periphery of the EL backlight and an upper luminous part is in a vicinity of center thereof.
Also, a preferable mode is one wherein the concave luminous parts are formed in the higher-density as the concave luminous parts come near the periphery of the EL backlight and are formed in the lower-density as the concave luminous parts come near the center of the EL backlight in the luminous layer of the EL backlight.
Also, a preferable mode is one wherein the concave luminous parts are larger as the luminance becomes lower and are smaller as the luminance becomes higher in the luminous layer of the EL backlight.
Also, a preferable mode is one wherein the concave luminous parts are larger as the concave luminous parts come near the periphery of the EL backlight and are smaller as the concave luminous parts come near the center of the EL backlight in the luminous layer of the EL backlight.
Also, a preferable mode is one wherein the concave luminous parts are formed in the high-density or the low-destiny at a predetermined range in the luminous layer of the EL backlight.
Also, a preferable mode is one wherein the concave luminous parts are small or large at the predetermined range in the luminous layer of the EL backlight. The predetermined range may be a character, a diagram, a symbol or a like. It is possible to make the luminance of only the predetermined range high or low.